Method for recovery of hydrocarbons from oil-bearing limestone or dolomite

Claim 1

A process for the recovery of liquid and/or gaseous hydrocarbons from an underground deposit of oil-bearing limestone or dolomite which comprises: (a) drilling at least two boreholes into the lower portion of said deposit from the earth's surface; (b) establishing communication between said boreholes within said deposit near the lower boundary of said deposit; (c) initiating combustion of the oil in said limestone or dolomite near the lower boundary of said deposit; (d) introducing an oxygen-containing gas into one of said boreholes and withdrawing gaseous combustion products from said oil from another of said boreholes until a sufficient amount of the alkaline earth carbonate in said deposit is decomposed into the alkaline earth oxide occupying a volume of from about 5 to about 30 percent of the volume of said deposit; (e) introducing water into one of said boreholes in such a manner that said water contacts said alkaline earth oxide without substantial mechanical agitation thereby disintegrating said alkaline earth oxide and forming an aqueous slurry containing alkaline earth hydroxide; (f) withdrawing said slurry of alkaline earth hydroxide through another of said boreholes thereby creating a cavity having a volume equivalent to from about 5 to about 30 percent of the volume of said deposit; (g) breaking down into said cavity the oil-bearing limestone or dolomite overlying said cavity until a rubblized zone extending vertically to a point near the upper boundary of said deposit has been formed; (h) establishing a flame front within said rubblized zone; (i) driving said flame front through said rubblized zone; and (j) withdrawing liquids and/or gases from said rubblized zone.